Production of fructose



NITED. STATES ratios PATENT "OFFICE,

WILLIAM C. ARSEM, OF SCHENECTADY, NEW YORK, ASSIGNOR TO INDUSTRIAL TECH-NICS CORPORATION, OF SCHENECTADY, NEW YORK, A. CORPORATION OF NEW YORK.

IRODUCTION or rnncrrosn.

ltoDrawing. Original application filed December 27, 1919, Serial No.347,797. Divided and this application filed AugustM, 1924. Serial No.731,965.

This invention relates to the production of fructose or fruit sugar froinulin-bearing plants, and particularly to the reduction of fructosefrom the roots of da lias.

5 I am aware that various investigators have described methods forproducing fructose from dahlia roots by extracting comminuted roots withwater, separating the inulin therefrom by various means, and then by ldrolizing the inulin so obtained to fructose by means of acids. When,however, these various methods are employed, a great many difficultiesare encountered in carrying out their processes, the yield of fructose lis wholly unsatisfactory for commercial purposes, and the productobtained in many instances is not sufiiciently pure for use as a foodproduct. One method heretofore used has been to extract the bulbs withwater containing a small percentage of calcium carbonate to obtain aneutral extract containing inulin, so that the latter is not hydrolizedby free organic acids, and then immediately, without furtherpurification,

2 separating the inulin either (1) by freezin the solution, allowin theice to melt, an

/filtering oii' the inulin, or (2) by immediately precipitatingtheinulin from the unpurified solution by the addition of alcohol,

to and finally hydrolizing the inulin thus obtained to fructose byheating with acid.

Now, I have found that when the process is carried out in any of theseways, the inulin which is separated at one stage of the process is notsuitable for further hydrolysis to fructose, because of the fact that itstill contains objectionable organic and inorganic impurities whichinterfere seriously with the conversion of the inulin to fructose andwith separating the fructose in solid or crystalline condition from itssolutions. Moreover, these processes are wasteful in that a largeproportion of the inulin is lost at various sta es in the process andcannot-be convenient y recovered, and also because the presence of theimpurities in the inuiin requires the use of such vigorous hydrolizingagents, that part of the fructose is decomposed and entirel lost.

Inulin is a carbohydrate 0 high molecular weight, nearly insoluble incold water, but very soluble in hot water. Upon complete hydrolysisityields of the monoses only fructose. It occurs widely distributed invarious plants, but, as a rule, only'in very small amounts, so that theisolation'of this product from most plants in a commercial way is notpracticable. It occurs in somewhat larger proportions in the class of.plants known as the Composites but in most of these also the amountpresent is too small for successful isolation by any commerciallypracticable process. In the roots of thechicory plant and in the rootsof the artichoke, and particularly in the large roots of the dahliaplant, inulin occurs in much greater amounts than in the other plants'yust mentioned, and by means of my process can recover the inulin fromthese plants in an entirely practicable manner, and in such a state ofurity that it can be readily converted by suhsequent steps inmy processinto fructose, which is an important food product. This last mentionedsugar, the production of which is the ultimate aim of my processpossesses many inherent advan-- tages over other sugars as an article offood.

For example, it is approximately sixty per i cent sweeter than ordinarycane sugar, and

nearly four times as sweet as glucose. It is also more palatable, havingno objection able characteristic flavor, such as some other su ars have.Its keeping qualities re good, eit er in the form of syrup or in 'ei'ystalline or powdered condition.

Moreover, fructose and also inulin' are highly beneficial as foods fordiabetics; For example, fructose maybe substituted for sugar as asweetening agent in various articles of diet used in the treatment ofdiabetic cases, without producing the harmful effects which are known toresult from cane sugar, lucose, and many other sugars. Likewise, wliileinulin' is not sweet and is practically tasteless, it may be used assuch without first h drolizing to fructose as a substitute for our inmaking bread, etc. Also, if desired, valuable food products may beformed without carrying the hydrolysis of the inulin to completion,because the incompletely hydrolized 'inulin is capable of forminggelatinous products somewhat similar to those made from ordinarygelatine and sold under certain trade-names, suchas Jello, etc.

In working out my process I have found that the inulin in the extractobtained from plants is in part associated with and in part chemicallycombined with certain impurities .these impurities are phosphates'ofalkalies,

of alkaline earths, and of alumina and probably compounds of organicacids with these same inorganic bases.- Inulin itself forms complexcompounds with some of these inorganic bases. For example, definitecompounds of inulin with barium have been prepared and are described inthe scientific literature pertaining to inulin. Hitherto the chemicalnature of these impurities has not been clearly recognized, and up tothe present the methods used have not effectively. removed them fromtheir combination with the inulin, so that when the latter ishydrolized, larger quantities of acids-are required to combine withthese impurities and to effect hydrolysis. I have found that theselarger quantities of acids bring about a decomposition of the inulin andalso of the fructose, resulting in serious loss of the food productswhich are the ultimate aim of my process. Also, the products formedcontain objectionable amounts of impurities.

Furthermore, I have found that successful hydrolysis of the inulin tofructose de-v pends to a very large extent upon an adj ustment of thehydrogen ion concentration to a range of values within very narrowlmits. If the concentration of hydrogen ion is too high, theobjectionable decomposition of the carbohydrates referred to above is aninevitable result. On the other hand, if the concentration of hydrogenion is too low, it is necessary to prolong the time of hydrolysis tosuch an extent that the slow decomposition of fructose which is normalltaking place all. the time during the hy rolysis, causes objectionableloss of the carbohydrates. Furthermore, I have found that the amount andnature of the inorganic impurities have a-pronounced effect upon theconcentration of hydrogen ion produced by the addition of a givenquantity of acid to the solution.

This effect results from the shifting of the equilibrium relationsbetween hydrogen ion and other ions present produced by the addition ofother ions to the system. For exam 1e, it is well known that theaddition of hydrochloric acid to a solution containing Ne l-1P0 resultsin' the production of NaHQPO with no appreciable'increase in thehydrogen ion concentration of the solution, since the deg ee ofdissociation of this las'tnamed salt is relatively-small as comparedwith hydrochloric acid. g

In addition to these inorganic impurities,

the objectionable effects of which have just been discussed, theextracts from the inulinbearing plants contain various organicimpurities which are in part combined not only With the inorganicimpurities, but some of which are probably combined directly with theinulin itself in such a way thattheir removal is rendered difiicult bythe application of any of the-hitherto known methods. As alreadymentioned, these organic impurities also interfere with the successfulhydrolysfsof inulin to fructose. This is probably due in part to theeffect they produce upon hydrogen ion concentration in' somewhat thesame way that the inorganic impurities produce this effect, but inaddition these or anic impurities also affect the properties 0 thefructose in a detrimental way. For example, they form soluble complexeswith the inulin and render it more difficult to precipitate fromsolution by means of alcohol, or by freezing. Likewise,

theseorganic impurities, unless removed, appear in the final product ofthe hydrolysis of inulin, increasing the hydroscopic properties offructose so that it may become lumpy, and also adversely affecting itskeeping qualities.

By my rocess I avoid all these difiiculties. Among 0t er means which Iemploy, I treat the extract containing the inulin with a weak base,preferably with ma nesium hydroxide, I

which are left in the solution by this treatment, are removed in a laterstep of my process in which the inulin after precipitation with alcohol(preferably about three volumes to one of solution) and then filtering,is washed first with concentrated alcohol to ,remove organic impurities,and then with cold water to remove water-soluble impurities, includingthe inorganic material. This step of my process is rendered moreeffective by first dehydrating the inulin, which I pre fer to do byheating the inulin solution or suspension after the addition ofalcoholfor a sufiicient length of time to partially dehydrate the inulinso that its subsequent washing can be carried out without danger ofserious loss due to its solution in the wash liquids. By the expressionto partially dehydrate I mean the removal of a limited amount of waterfrom the suspended or colloidally dissolved inulin whereby the inulin iscoagulated to a definite degree,

iterates filter and yet is sutliciently porous or granudid lid

lar free from horny masses to promote the percolation of the waterthroughut the precipitated material. Dehydration in this sense isdistinguished from ordinary drying mainly by the fact that horny massesare avoided. In my process I prefer to adjust the "concentration of thealcohol used in precipitating the inuhn to sucha value that it aids inthe dehydration of the inulin to the required degree. The concentrationwhich I particularly prefer is approximately three volumes of alcohol toone of solution. By another modification of my method I digest theinulin after precipitation with alcohol with approximately ninety-fiveper cent alcohol at an elevated temperature and for a sulficient lengthof time to bring about the desired dehydration. After the treatment theinulin upon drying is left in a powdery dry condition, instead of in theform of a more or less horny mass which is produced when the inulin isdried without this partial dehydration. It will be understood that theproportions of alcohol employed in bringing about th s dehydration andthe time and temperature may be varied to a certain extent withoutdeparting from my invention.

Having described the most important features of my invention, I shallnow give a detailed description of the exact mode and manner in which myprocess may be carried out in a practical manner. It will be understood,however, that this description is given as an example of one of themodes of my process, and that my invention is not confined to the exactdetailed description of the processes as set forth.

I take 750 pounds of dahlia bulbs, rated very fine, 1,000poundsof waterwhic ma or may not be purified, clarified or distille and heat themixture one hour at to (1, then filter, add 100 pounds magnesiumhydroxide suspension containing approximately 5 per cent magnesiumhydroxide and heat until the temperature reaches "100 C. At this point Imay pass carbon dioxide through it for twenty minutes, or untilabsorption is complete while maintaining the temperature at 100 C. Thetemperature is then maintained at 100 C. without continuing to' passcarbon dioxide until excess carbon dioxide is expelled. Whether or not Ihave treated the mixture with carbon dioxide, Tnow filter the extract,evaporate it to 25 or 30 per cent concentration of inulin, add threetimes its volume of methyl or -ethyl alcohol of approximately per centstrength, keep the solution hot, preferably by boiling it in a vesselrovided with a condenser toavoid loss of a cohol, then allow it to coolthoroughly. During this series of normal.

steps the inulin, together with various inorganic and organicimpurities, is extracted from the dahlia bulbs, the milk of magnesia ormagnesium hydroxide decomposes, coagulates and precipitates aconsiderable percentage of the impurities, both inorganic and organic;the carbon dioxide sets tree some inulin which may be carried down withthemagnesia sludge and also releases some weak organic acids from theirmagnesium compounds. The cold liquid, from which inulin has separated ina dense, slightly hydrated form, is filtered and the cake of inulin fromthe filter'press is washed first with an alcohol to removealcohol-soluble iimpurities and then with purified or distilled water toremove water-soluble impurities, particularly inorganic salts. Theurified inulin in the filter press is now disso ved by pumping in hotpurified water and the solution is filtered if necessary. At this pointthe solution contains inulin in a very pure form with mere traces ofimpurities and should be brought to a concentration of ap anyappropriate manner, as for example, by titrating a sample with alkali,using an appropriate indicator; by measuring itselectrical conductivity;or by measuring the hydrogen ion concentration directly by means of astandard hydrogen electrode.

The solution is now heated to C. and kept at this temperatureapproximately one hour, or until appropriate tests have shown Theacidity may be determined in that the conversion of inulin to fructosehas takcnplace to such an extent that the maximum yield will be obtainedand further action of the acid is stopped by -adding an equivalentamount of sodium'carbonate, sodium bicarbonate, or calcium carbonate.

Instead of using hydrochloric acid to tun nish the hydrogen ionconcentration necessary to catalyze the hydrolysis of inulinll may useinstead phosphoric acid, sulphuric acid, hydrofluoric acid, sulphurousacid, oxalic acid, formic acid, nitric acid, acid salts such as sodiumbisulfate, sodium bisulfite, dihydrogen sodium phosphate or salts ofstrong acids with-weak bases which hydroly ze easily and will yield theproper hydrogen ion concentration. Examples of the latter are anilinehydrochloride, aluminum chloride, etc. The advantage oil some of thesealternative sources of hydrogen ions solution of fructose in a vacuumevaporator,

and in doing this I may either carry evaporation only far enough toproduce a syrup of a marketable consistency and sweetness, or I maycontinue the evaporation to dryness using for the final step inevaporation a vacuum drum .dr er, or similar apparatus, which will yielfructose as a dry powder or in the form of thin scales having thestrength, sweetness and other valuable properties of fructose. If Idesire to produce fructose in the crystalline form I may proceed ineither of two ways. i

I may. concentrate the syrup above described until it has reached asupersaturated condition and then induce crystallization by addingfructose crystals while continuing to evaporate under reduced pressureas crystallization progresses. I may stop the evaporation while someliquid still remains and separate the crystals from the mother. liquorby filtration or centrifugal draining. Or, I may allow the evaporationto continue until the entire amount of fructose is obtained in a drycrystalline form.

Instead of obtaining crystals by concentrating the syrup, seeding andevaporating as above described, I may concentrate the syrup almost todryness, dissolveit in 5 to 1.0 parts of absolute alcohol, allow thesolution to cool, withdraw the clear upper layer which is asupersaturated solution of fructose in alcohol and recover the fructosein crystalline form by adding some crystals of fructose to thissupersaturated solution and agitating until crystallization is complete.The lower layer which has separated from the clear upper layer, asjuststated,"is treated with the mother li nor from the fructosecrystallization or with a fresh portion of absolute alcohol, heated,allowed to cool and the upper clear supersaturated layer treated torecover fructose crystals as just, de'-' scribed.

This application is a division of my copeuding application Serial No.347,797.

I claim: 1. The method of preparing fructose froi inulin which comprisestreating a solution containing the purified inulin with sufficient acidto produce a concentration of hydrogen ion approximately equivalent toone-hundredth normal, and keeping the solution at an elevatedtemperature, until the desired conversion to fructose is obtained.

2. The method of preparing fructose from inulin which .comprlsestreating a solution containing the same with sufficient acid to combinewith the small amount of basic impurities present, both organic andinamount of basic impurities present, both organic and inorgamc, and toproduce a hydrogen ion concentration of approximately .01 normal andthen heating the inulin to convert to fructose and neutraliz- 1 ing theacid as soon as the maximum possible conversion to fructose has beenobtained.

4. The process of preparing fructose from inulin which comprisestreating a solution containing inulin with a compound capable ofyielding hydrogen ions in a suflicient amount to combine with the smallamount of basic impurities present, both organic and inorganic, and toproduce a hydrogen ion concentration of approximately .01 normal, thesaid compound having a catalytic action upon the hydrolysis of inulinbut being sub; stantially inactive as a catalyst in the decomposition offructose, heating the solution of inulin to convert it to fructose andneutralizing the acidity as soon as the maximum possible conversion tofructose has been obtained.

5. The method of preparing. fructose from inulin which comprisestreating a solution containing the purified inulin with sufficient acidto produce a concentration of hydrogen ion approximately equivalent to.01 normal, keeping the solution at an elevated temperature until thedesired conversion to fructose is obtained, treating the fructosesolution with charcoal, filtering, concentrating the filtrate andseparating out fructose from the concentrated filtrate.

6. A method of preparing fructose from inulin which comprises treating asolution containing the same with sufficient acid to combine with thesmall amount of basic impurities present, both organic and inorganic,and to produce a hydrogen ion con centration of approximately .01normal, then heating the inulin to convert to fructose, neutralizing theacid as soon as the maximum. possible conversion to fructose has beenobtained, treating the solution with charcoal, filtering, concentratingthe filtrate,

and separating out fructose from the concentrated filtrate. g I

In testimony whereof I aflixmy signature.

WILLIAM C. ARSEM.

